An analysis of non-propagating fatigue cracks

An analysis for the formation of nonpropagating fatigue cracks at (the base of V-shaped) notch roots, based on the considerations of the extent of the critically stressed region ahead of a notch or a crack tip, and the resulting volumetric strength effect, is developed. Assuming that the minimum local cyclic stress required for crack initiation from a notch root is equal to the unnotched fatigue limit, σ_e, and that the minimum local cyclic stress required for the propagation of the crack is equal to the theoretical strength of the material, σ_e, a model of notch fatigue limit is proposed that shows that nonpropagating cracks should form at the notch base if ρ≤ ρ⁰, a critical root radius, provided the notch is sufficiently deep,i.e. d ≥ ρ₀. The radius ρ₀ is a material constant and can be estimated from known material properties. The estimated values of ρ₀ are in fairly good agreement with available experimental values for steels and pure copper. For stresses near the notch fatigue limit it is suggested that p₀ be regarded as a radius above which notch fatigue limit is essentially initiation controlled and below which essentially propagation controlled. The notch fatigue limit based on complete fracture can then be estimated more accurately with mild as well as sharp notches. D. N. LAL, formerly a Graduate Assistant in Materials Science, Syracuse University     

Über die Basizität flüssiger Schlacken der Systeme CaO–SiO2 und CaO–Al2O3

EMK-Messungen mit einer Diffusionszelle an flüssigen Schlacken der Systeme CaO–Al₂O₃ und CaO–SiO₂ bei 1600°C. EMK und Sulfidkapazität zeigen lineare Abhängigkeit. EMK-Werte können als relatives Basizitätsmaß gewertet werden.     

In search of novel water soluble forskolin analogues for positive inotropic activity

Using the novel lead from hydroxy acetyl substituted forskolin analogues, such as 7 beta-hydroxyacetyl-7 beta-deacetyl forskolin or 6 beta-hydroxyacetyl forskolin, a number of water soluble omega-amino acyl derivatives were synthesized. Two such compounds 6 and 18 showed better in vitro activity but failed to show in vivo activity.     

Studies on thermodynamic compatibility of nitrile rubber and polybutadiene by inverse gas chromatography

Inverse gas chromatography technique has been used to study the thermodynamic compatibility of the industrially important elastomers polybutadiene (BR) and polybutadiene copolymerised with acrylonitrile (NBR). The NBR used in this study had nitrile contents of 18 and 34%. The ratio of BR/NBR in blends varied between 1 and 0.25 in both cases and retention volume of twelve probes was measured at 80°C. The Flory-Huggins interaction parameter X′₂₃, computed using a standard procedure, and also the interaction parameter B₂₃ showed that BR and NBR are incompatible in all compositions and that incompatibility increases with nitrile content. © 1995 John Wiley & Sons, Inc.     

A study of the new K2NiF4-type solid solutions Sr2FexRu1−xO4 by Mőssbauer spectroscopy and other techniques

The magnetic and structural properties of the solid solutions Sr₂Fe_xRu_1?xO₄ (O ? x ? 0.5) have been studied using ⁵⁷Fe and ⁹⁹Ru Mőssbauer spectroscopy and other techniques. These phases, which are reported for the first time, have the K₂NiF₄-type structure with iron and ruthenium distributed at random on the B-site. As the ruthenium is replaced by iron the weakly-metallic conductivity and Pauli paramagnetism of Sr₂RuO₄ give way to localized-electron behaviour and long-range antiferromagnetic order despite the layer-type structure which is unfavourable for 180° Ru-O-M (M = Fe or Ru) magnetic exchange interactions in three dimensions. For x = 0.1-0.4 the iron is present almost entirely in the +3 oxidation state, but for x = 0.5 appreciable amounts of Fe^IV are also present, in conjunction with Fe^III, Ru^IV, and Ru^V.     

Enhanced specificity of truncated transmembrane protein for serologic confirmation of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2 infections by western blot (immunoblot) assay containing recombinant envelope glycoproteins

Immunoassays based on the highly immunogenic transmembrane protein of human T-cell lymphotropic virus type 1 (HTLV-1) (protein 21c) are capable of detecting antibodies in all individuals infected with HTLV-1 and HTLV-2. However, because of antigenic mimicry with other cellular and viral proteins, such assays also have a large proportion of false-positive reactions. We have recently identified an immunodominant epitope, designated GD21-I located within amino acids 361 to 404 of the transmembrane protein, that appears to eliminate such false positivity. This recombinant GD21-I protein was used in conjunction with additional recombinant HTLV type-specific proteins and a whole virus lysate to develop a modified Western blot (immunoblot) assay (HTLV WB 2.4). The sensitivity and specificity of this assay were evaluated with 352 specimens whose infection status was determined by PCR assay for the presence or absence of HTLV-1/2 proviral sequences. All HTLV-1-positive (n = 102) and HTLV-2-positive (n = 107) specimens reacted with GD21-1 in the HTLV WB 2.4 assay, yielding a test sensitivity of 100%. Furthermore, all specimens derived from individuals infected with different viral subtypes of HTLV-1 (Cosmopolitan, Japanese, and Melanesian) and HTLV-2 (IIa0, a3, a4, IIb1, b4, and b5) reacted with GD21-I in the HTLV WB 2.4 assay. More importantly, HTLV WB 2.4 analysis of 81 PCR-negative specimens, all of which reacted to recombinant protein 21e in the presence or absence of p24 and p19 reactivity in the standard WB assay, showed that only two specimens retained reactivity to GD21-I, yielding an improved test specificity for the transmembrane protein of 97.5%. None of 41 specimens with gag reactivity only or 21 HTLV-negative specimens demonstrated reactivity to GD21-I. In an analysis of additional specimens (n = 169) from different geographic areas for which PCR results were not available, a substantial increase in the specificity of GD21-I detection was demonstrated, with no effect on the sensitivity of GD21-I detection among specimens from seropositive donors. Thus, the highly sensitive, GD21-I-based HTLV WB 2.4 assay eliminates the majority of false-positive transmembrane results, thereby increasing the specificity for serologic confirmation of HTLV-1 and HTLV-2 infections.     

Acute coronary occlusion during early post-PTCA exercise testing: a rare but avoidable risk

We describe here one instance of an acute occlusion of an angioplastied LAD coronary artery occurring during a treadmill stress test performed 2 d after the procedure. The occlusion occurred during the recovery period after a reasonably high level of stress was achieved without evidence of ischaemia. Similar instances described in the literature are summarized and discussed. In the light of these data, it might be prudent to avoid early post-PTCA exercise stress testing.     

Necessary and sufficient number of parity checks in codes correcting random errors and bursts with weight constraints under a new metric

A new metric, called the class metric, has already been introduced by Sharma and Kaushik. In this paper, we obtain extensions of Hamming sphere packing and Varsharmov-Gilbert-Sacks bounds to codes correcting random errors and bursts with weight constraints under the class metric.